In imaging devices, such as printers, feeding sheets individually from external of the imaging device allows selection of individual sheets having unique characteristics, such as letterhead or preprinted borders, or selected width. It is common to either simply provide a slot leading to the sheet transport mechanism of the device or to provide an external tray on which the sheet is slid across so as to be more reliably positioned in the sheet transport.
Reliably positioning the sheet is important because, if the sheet sags against the imaging device structure, the sheet may not feed evenly. When the sheet sags against the device an uneven frictional drag can occur and the sheet enters the sheet feed mechanism turned from the intended position. Accurate registration of the sheet is then lost and not normally recovered, and the final image is turned from the correct position. In extreme cases the sheet jams within the printer.
In those devices in which no guide structure is provided, entire reliance is on the careful insertion of the sheet by the operator. Experience indicates that defective insertions will occur fairly frequently, especially with new operators.
Those devices that have a guide tray are generally effective in achieving proper insertion of the sheets. However, such guide surfaces necessarily extend from the side of the imaging device during use. To avoid such extension being permanent and thereby always defining a perimeter of the imaging device, the guide trays are generally thin structures, which slide into or out of the imaging device or fold out from the device or otherwise need to be positioned by the operator. Such operator intervention reduces productivity and requires some training of the operator. The tray structures themselves add cost to the imaging device, and, since they are thin and relatively unprotected, they are subject to damage.